The Chinese city of Dandong is cracking down on smuggling and other activity through which COVID-19 could enter from outside, municipal authorities have stated, amid apparent concerns that North Korea’s outbreak could spill over to the border city.

As Dandong deals with its own COVID-19 outbreak, the city government said in a press conference on Sunday that officials have had trouble breaking the chain of infections and finding a “clear epidemiological correlation” for positive cases.